Java Generics and Collections, 2nd Edition

Chapter 5. Reification

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By the time that generics were introduced to Java, eight years after version 1.0 shipped, there were many millions of lines of code already in use in commercial applications. It is a tribute to the design of generics that the introduction was so successful, resulting in gradual generification of all major libraries and most client code within a few years, without major compatibility problems. How this was achieved is described in [Link to Come]. The key to its success was erasure, without which Java as we know it today could not exist. Legacy code makes no distinction between List<Integer> and List<String> and List<List<String>>, so erasing parameter types is essential to easing evolution and promoting compatibility between legacy code and new code. But everything comes at a cost, and in this chapter we must settle our debts.

The Oxford English Dictionary defines reify thus: “To convert mentally into a thing; ...